Inverted image multibeam cathode ray tube

ABSTRACT

An electron gun within a glass envelope simultaneously emits a plurality of coplanar electron beams through corresponding apertures in a concave shaped electrode. The apertures are arranged in a single row along a vertical diameter of the concave electrode in the case where the sweep lines developed by the electron beams on an output phosphor screen are in a horizontal direction. A like plurality of grids are positioned between the concave electrode and a cathode, and are aligned with the concave electrode apertures. Input signals simultaneously applied to the grids produce intensity modulation of the electron beams. An anode positioned between the concave electrode and phosphor screen accelerates the electron beams along straight cross-over paths to provide an inverted image on the screen. Deflection coils or plates positioned between the anode and screen simultaneously deflect all the electron beams in the sweep direction whereby the input signals can be simultaneously displayed.

United States atent [191 Houston lNVERTED IMAGE MULTIBEAM CATHODE RAY TUBE [75] Inventor: John M. Houston, Schenectady,

[73] Assignee: General Electric Company,

Schenectady, N.Y.

[22] Filed: Sept. 1, 1972 [21] Appl. No.: 285,912

Primary Examiner-Roy Lake Assistant ExaminerSiegfried H. Grimm Attorney-J0hn F. Ahern et al.

[ Dec. 11, 1973 [57] ABSTRACT An electron gun within a glass envelope simultaneously emits a plurality of coplanar electron beams through corresponding apertures in a concave shaped electrode. The apertures are arranged in a single row along a vertical diameter of the concave electrode in the case where the sweep lines developed by the electron beams on an output phosphor screen are in a horizontal direction. A like plurality of grids are positioned between the concave electrode and a cathode, and are aligned with the concave electrode apertures. Input signals simultaneously applied to the grids produce intensity modulation of the electron beams. An anode positioned between the concave electrode and phosphor screen accelerates the electron beams along straight cross-over paths to provide an inverted image on the screen. Deflection coils or plates positioned between the anode and screen simultaneously deflect all the electron beams in the sweep direction whereby the input signals can be simultaneously displayed.

21 Claims, 3 Drawing Figures lOct FROM SWEEP GENERATOR PAIENIEDMH ma I 3.778.659

SQUIRE FROM SWEEP Y WAEMGE GENERATOR 1 v0 l5 -+v "Q (INPUT SIGNAL FROM SWEEP GENERATOR INVERTED iMAGlE MULTIBEAM CATHODE RAY TUBE My invention relates to a visual display device wherein a plurality of electron beams are simultaneously swept across the output phosphor screen of the device to generate one display frame per sweep, and in particular, to a device wherein the plurality of beams are formed in an electron gun and the visual image on the output screen is inverted relative to the electrical input signals which produce the image.

There are many applications for high-speed, highbrightness visual displays of information in two dimensions simular to those of television, but being presented at much higher speed. The use of a single-beam display tube, such as is utilized in television and conventional cathode ray tubes for the higher speed applications results in a severe limitation of the display brightness that can be produced due to the necessarily higher required sweep (scan) speeds, as well as placing stringent frequency response requirements on the display tube input video circuits.

In certain applications, the recent development of miniature sensor devices permits the fabrication of an apparatus comprising a linear array of such sensors which may be ultrasonic piezoelectric detectors or infra-red detectors as two examples. A single scan of such linear array obtains the two-dimensional information required for the display, the output (versus time) of each sensor being associated with a corresponding sweep line on the display tube. The single row of sensors, which may number 100 as one typical example, are simultaneously responsive, but the advantage of such simultaneous operation is obviously limited if the detected signals must be stored and then displayed sequentially, as when utilizing a conventional line-by-line scan single-beam cathode ray tube.

A specific example of an apparatus embodying the above-described single row of multi-sensors is described in a concurrently filed patent application S.N. 285,910, entitled Method and Apparatus for Visual Imaging of Ultrasonic Echo Signals Utilizing a Single Transmitter, inventors John M. Houston and Jack D. Kingsley, and assigned to the assignee of the present invention. Such apparatus may be utilized in medical diagnostics in the examination of human organs undergoing motion, such as a beating heart, and the row of sensors (of the ultrasonic transducer type) are positioned parallel to the front of the patient when obtaining a visual display of a planar slice through the heart from front to back. Each transducer may receive several ultrasonic echo signals at various times corresponding to acoustic heterogeneities internal of the heart at various depths therein. Due to the motion (beating) of the heart, the ultrasonic echo signals must be generated at sufficiently rapid rate to obtain reasonable resolution of the displayed image and an image that appears flicker-free to the eye of the observer. Although a visual display of the output (versus time) of a row of many simultaneously responsive transducers in which the information signals arrive at a rapid rate, and resulting from a sequential read-out of the transducers which is then presented as a serial input (Iine-by-line scan) on a single-beam cathode ray tube, may be satisfactory, it may be desired or necessary to eliminate the signal storage step and thereby obtain a more rapid presentation of the display, or increased image brightness.

Therefore, one of the principal objects of my invention is to provide a new visual display device which has a high speed of operation.

Another object of my invention is to provide a device which obtains a high brightness of the visual display thereon.

A further object of my invention is to provide the device with a plural signal input for simultaneously displaying the outputs of a like plurality of sensors which develop the input signals without the need for memory circuits or other special signal processing.

Briefly stated, and in accordance with my invention, I provide a visual display device of the multi-beam type in that the sweep or scan lines on the output screen thereof are simultaneously generated. The sweep lines are generated by simultaneously deflecting a like plurality of coplanar electron beams simultaneously emitted through a like plurality of apertures in a concave shaped electrode supported within the sealed envelope of the device. A single electron source in close proximity to the concave electrode supplies the electrons to form the beams, and a like plurality of grids positioned between the electron source and apertured concave electrode provide intensity modulation of the electron beams in accordance with the various input signals simultaneously applied to the grids. An anode causes acceleration and focussing of the electron beams andinversion of the resultant visual image on the screen relative to the input signals. An electrostatic or electromagnetic means positioned between the anode and output phosphor screen provides the simultaneous deflection of the electron beams to obtain the desired simultaneous sweeps across the phosphor screen whereby the input signals can be simultaneously displayed.

The features of my invention which I desire to protect herein are pointed out with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like parts in each of the several figures are identified by the same reference character, and wherein:

FIG. l is an elevational sectional view of a preferred embodiment of my multi-beam cathode ray tube;

P16. 2 is an enlarged front view, partly broken away, of the concave electrode depicted in side view in FIG. 1, and

FIG. 3 is an enlarged view of the electron gun portion of the device depicted in FIG. 1.

Referring now in particular to FIG. 1, there is shown a preferred embodiment of my multi-beam cathode ray tube invention which is comprised of a sealed tubular member if) typically of cylindrical form of a type similar to that employed in conventional cathode ray tubes. Thus, member Ml may be a glass envelope having an input end 10a near which are located the electron beam forming elements (electron gun), and an output end 1% along which inner surface thereof is deposited or otherwise formed an output phosphor screen 13. Member 10 may also be formed of other materials such as a ceramic or other electrically insulating, nonmagnetic material which is compatible with a pressure in the order of 10' torr pressure or lower. Although tubular member 10 is illustrated as being of constant diameter, it can be of varying diameter, and in particular,

the output end b can be of larger or smaller diameter than the input end 10a as required by the particular circumstances of the application.

The electron beam forming elements (electron gun) of my visual display device comprises a major portion of my invention and provides a means for simultaneously generating a plurality of coplanar electron beams. The electron gun consists of a concave shaped electrode 11 which is supported near the input end 10a of tubular member 10, and a suitable uniform source of electrons 12 positioned in close relationship to concave electrode 11 on the side thereof closer to the input end 100 of tube 10. Concave electrode 11 is preferably of circular form as indicated in the front view thereof in FIG. 2, and the circumferential edge thereof may be in contact with the side wall of tubular member 10, or slightly spaced therefrom. Electrode 11 is firmly supported within tubular member 10 by any suitable means such as a plurality of two or more electrically conductive members forming small tabs 11a connected preferably in equally spaced apart relationship along the periphery of electrode 11 and also connected to the sidewall of tube 10. One of such tabs is connected to a suitable terminal 11c passing through the tube 10 sidewall for connection to a suitable voltage source +V for maintaining concave electrode 11 at a slightly positive potential relative to electron source 12. Concave electrode 11 is formed of an electrically conductive, nonmagnetic material which is easy to fabricate such as nickel, stainless steel, aluminum, or Monel metal (an alloy of nickel, copper and possibly other metals). Concave electrode 11 is preferably of constant thickness, especially along the (vertical) diameter along which are formed a single row of equally spaced apart, equal diameter apertures 11b of number equal to the number of sweep lines to be produced on the output phosphor screen 13. For a vertical orientation of the row of apertures, the sweep lines are in a horizontal direction. For purposes of visualization of the orientation of the various elements of my apparatus, the longitudinal (centerJine) axis of my device is designated as the Z-axi's and the vertical direction along which the electron beam apertures 11b are formed through concave electrode 11 is designated as the Y-axis. The axis perpendicular to the plane defined by the Y and Z axes is designated as the X-axis (and which becomes the direction in which the electron beams are swept or deflected across the face of phosphor screen 13).

For most applications, there would be a minimum of sweep or scan lines simultaneously developed on the output phosphor screen 13 in order to obtain a reasonable image resolution, thereby requiring at least a corresponding 20 apertures 11b formed through concave electrode 11. However, I visualize the use of considerably more than 20 apertures (and corresponding sweep lines) in most applications, a general application having in the range of 50 to 100 sweep lines and an upper limit of approximately 1,000, the number of sweep lines being governed primarily by the desired resolution and size of the visual display to be presented as well as by the diameter size of concave electrode 11 and the ability to fabricate closely spaced apertures therethrough. The apertures 11b are formed substantially across the entire diameter of the concave electrode as depicted in FIG. 2 and preferably are of circular outline, although they can be of other shapes if desired. The uniform electron source means 12 positioned behind concave electrode 11 is oriented to be in overlapping relationship with the apertures llb. Although the electron source 12 may be independently supported from the side walls of tubular member 10, a more practical arrangement consists of source 12 being supported and electrically insulated from concave electrode 1 l by any suitable means such as a plurality of mica or other electrically insulating cylindrical members of small size attached along the outer portions of the electrical source means 12 and the adjacent inner portions of concave electrode 11 but spaced from apertures 11b. Electron source 12 is a single elongated cathode which may be in the form of a directly or indirectly heated electron emitting strip extending along the apertured diameter of concave electrode 11 and is of sufficient width to extend slightly beyond the apertures 11b. In one convenient form, electron source 12 is an oxide-coated nickel tubing of oval cross section with a heater inside similar to that employed in prior art radio receiver tubes. Alternatively, and less preferably, cathode 12 is a directly heated oxide-coated ribbon, but in such case the operating voltage must be small compared to that of the operating voltages of concave electrode 11 and the grid electrodes positioned between elements 11 and 12. The oxides utilized in the cathode may be the conventional mixtures of the oxides of barium, strontium and calcium. The thermionic electron emitter 12 preferably is bent in a slight curve to conform to the curvature of apertured electrode 11. In the case of an indirectly heated thermionic emitter, the electron emitting outer element is assumed to be at zero potential and the inner heater element 12b is connected to a power supply operating at a low voltage iV (typically 1: 6 volts), the ends of the heater element being brought out through opposite portions of the side wall of tubular member 10, or alternatively, one end of the heater 12b is connected to the outer element 12a and the other end is brought out to a 12 volt supply.

A conventional anode in the form of a truncated con ical electrically conductive member 14 is located axially approximately half the distance between the cathode 12 and phosphor screen 13 and provides electrostatic acceleration and focussing of the electron beams which pass through the apertures 11b in concave electrode 11 in their coplanar (in the absence of beam deflection) paths to phosphor screen 13. Anode 14 is cylindrically symmetrical about the Z-axis and is supported at the side wall of tubular member 10. A suitable terminal is provided through the side wall for application of a voltage +V for operating the anode at a relatively high positive potential relative to the cathode. In general, the phosphor screen 13 is operated at the same potential as anode 14. The combination of cathode 12, concave electrode 11, anode l4 and phosphor screen 13 is similar to the electron-optics in a conventional electrostatically focussed optical image intensifier tube having crossover optics but is unconventional for a cathode ray tube. The shapes of concave electrode 11 and anode 14 with their applied voltages +V,, +V develop equipotential lines which are concentric spherical surfaces to a good approximation such that the electron beams passing through the apertures 11b in concave electrode 11 travel in straight lines toward the sphere centers and thus crossover in the region of the anode center. Since anode 14 and phosphor screen 13 are operated at the same voltage, once the electrons reach the region beyond anode l4 they enter an essentially field-free region and therefore continue in straight line paths to form a resultant inverted visual image on phosphor screen 13 in response to input electrical signals applied to control grid electrodes to be described hereinafter. Three of the electron beam paths are depicted by dashed lines passing from concave electrode 11 to phosphor screen 113 and have a common crossover point along the centerline (Z) axis in the region of anode 14. Phosphor screen l3 may be a layer of any suitable phosphor material typically utilized in cathode ray tubes such as zinc cadmium sulfide willemite or zinc oxide.

In the absence of any control of the electron beams, the plurality of beams would all remain in the Y-Z plane (including the centerline axis of the device). However, the electron beams are simultaneously deflected in the X-axis direction to produce the (horizontal) line scans or sweeps on the phosphor screen 13 by means of a pair of deflection coils 15 located between anode l4 and phosphor screen 13 and supported along the outer surface of tubular member it) as depicted, or may be supported along the inner surface thereof, to provide electromagnetic deflection of the electron beams in the X-axis direction. The alternating magnetic field generated by deflection coils 15 is indicated by the arrows designated B and both coils are energized from opposite polarity ouputs of a conventional sweep generator to provide the same directional magnetic fields across the interior of tubular member 110 in the Y-axis direction. Deflection coils 115 are conventional pancake type coils each circumscribing slightly less than half of the circumference of tubular member 10. The coils can be fabricated of enameled copper wire as one typical example. Alternatively, electromagnetic deflection coils 15 can be replacedby a pair of electrostatic deflection plates supported interior of tube It) to provide the electron beam sweep or scan function. Thus, it can be seen that the plurality of electron beams are simultaneously swept across the phosphor screen thereby overcoming the lower speed display (or same speed but much lower display brightness and stringent frequency response requirements on the input signal circuits) associated with serial (line-by-line) scans produced with single-beam cathode ray tubes. In the general case wherein apertures 11b are equally spaced apart in concave electrode 11, the parallel sweep lines appearing on phosphur screen R3 are also equally spaced apart.

The visual image formed on phosphur screen 13 results from electrical signals obtained from a plurality of signal sources such as simultaneously responsive sensors which, as mentioned hereinabove, may be a single row of ultrasonic transducers utilized in an apparatus for medical diagnostic applications such as the examination of the beating human heart with the ability of viewing its motion as well as internal portions thereof such as the valves, arteries, etc. The visual image is obtained on the phosphor screen 13 by intensity modulation of the electron beams in accordance with the electrical input signals obtained from the transducers which are time-discriminated, that is, each transducer may develop several signals at slightly different times corresponding to the ultrasonic echo signals received from different depths of the heart. It is assumed that the plurality of transducers is equal in number to the plurality of apertures llb through concave electrode 11, that is, each electron beam is associated with a corresponding transducer. The input electrical signals (from the transducer outputs) are supplied to a single row of a like plurality of control grids 16 positioned between cathode 12 and apertured concave electrode 11 such that the transducer voltage signals applied to each particular grid intensity modulates the electron beam passing through the corresponding aperture 11b of concave electrode ill. The grids 16 are thus located behind corresponding apertures Hb in alignment with the electron beam axes, and preferably are mounted on concave electrode 11 by means of small insulators. An insulated electrical conductor 16a is connected to each grid and second ends of such conductors are connected (such as by spot-welding) to separate terminals 16b passing through the sidewall of tube 10 and preferably symmetrically arranged around the circumference thereof. The separate grid terminals have the advantage of providing a lower electrical capacitance. Alternatively, the grid conductors 16a may be bundled together in insulated relationship and passed through the side wall of tubular member 10 as one thick multiconductor member but this approach may present difficulties in accomplishing as well as increasing the capacitance. The grids are electrically conductive members and may be in any convenient form such as a small washer as used in conventional cathode ray tubes or a small piece of nickel mesh which is commercially available with a one mil period and percent transparency. Assuming a beam cathode ray tube with a circumference of 4.5 inch, the 100 grid terminals 16b are symmetrically arranged to be mils apart which presents no problem in fabrication. The multibeam cathode ray tube preferably mates with a socket also having 100 connections for supplying the electrical input signals to the grids. This specific example of my multibeam cathode ray tube would thus be utilized to display the output (versus time) of a single row of 100 sensors wherein each (ultrasonic) sensor or transducer receives information (ultrasonic echo signals) at rates as high as several separate signal levels per microsecond at which speed a conventional single-beam cathode ray tube is incapable of displaying such rapidly formed information, at least not without an intermediate, time-consuming, signal storage step. Thus, signals which may be arriving simultaneously at the grid 16 inputs of my multibeam cathode ray tube from different transducers can be simultaneously displayed, a capability not possible for a single-beam tube.

One or more cylindrically symmetrical electrostatic electrodes 17a and 17b may be supported within tubular member Ml between apertured concave electrode 11 and anode M for supplying the correct boundary conditions to improve the concentricity of the spherical equipotential lines between electrode 11 and anode 14. These focus electrodes 17a and 17b are operated at potentials intermediate the potentials of aperture electrode 11 and anode 14 relative to cathode l2 and also aid in focussing the output image upon phosphor screen 13 since some of the electrons inherently may have small transverse velocities. Focus electrodes 17a and 17b may have any of a number of shapes and may be positioned along the inner surface of tubular member 10 or spaced inwardly therefrom in order to obtain the desired electric field effect. Positive voltages +V and +V are applied to focus electrodes 17a and 17b respectively, by means of suitable terminals passing through the sidewall of tube M).

The single row of apertures lllb are formed through concave eldctrode 11 by any suitable fabrication technique compatible with the material utilized. Thus, the holes may be drilled or chemically etched, as two typical methods of hole fabrication. In the case of the 100 beam apparatus, and assuming concave electrode 11 is of 4 inch diameter, the holes would be approximately 40 mils apart and approximately 15 mils in diameter. The grid leads 16a are then connected to grids l6 and their associated terminals 16b and the tube envelope is then evacuated to the desired vacuum through the input end 1011 and sealed circumferentially along 100 near the tube input end. For the particular size tube and apertured concave electrode described hereinabove, the thermionic cathode 12 is 4 inches long and approximately 20 mils wide to thereby adequately overlap the IS mil diameter apertures 11b. The input signals applied to the grid 16 are in the voltage range from O to l() volts and apertured concave electrode 11 is operated at a positive voltage in the range of to 20 volts which is sufficiently positive to obtain a maximum beam current of approximately I microampere through any one hole in the apertured electrode. Focus electrodes 17a and 17b are operated at voltages typically a small fraction of the anode voltage, i.e., usually one-fourth or less, and the focus voltages are adjusted to maximize the focus and minimize the distortion of the visual image appearing on phosphor screen 13. The anode and phosphor screens are operated at equal positive voltages in the range of 5 to 25 kilovolts. The typical maximum current of l microampere per electron beam, or a maximum of 100 microamperes for a 100 beam tube, and such total tube current is sufficient to yield adequate brightness on a phosphor screen approximately 4 inches in diameter. A maximum current of l microampere per beam requires a cathode current density of approximately 1 milliampere per square centimeter for a l5 mil aperture lllb in electrode 111.

As stated hereinabove, although the phosphor screen 13 is illustrated as being of approximately the same di mension as the apertured concave electrode Ell, it can be larger or smaller, as desired. Thus, a larger diameter output end 1012 of tube M1 permits the use of a larger phosphor screen to thereby obtain a larger visual image. alternatively, a smaller diameter input end a of tube 10 permits a reduction in the size of the apertured electrode El relative to phosphor screen 13, resulting in the advantage of reducing the size and power requirements of the deflection coils but has the disadvantage of reducing the hole-to-hole spacing in electrode 11 and thus increasing the difficulty of hole fabrication.

An additional feature which may be added to my multibeam cathode ray tube is the incorporation of a pair of electrostatic deflection plates l8 positioned in the electric-fieldfree region between anode 14 and phosphor screen 13, and preferably betwen anode 14 and deflection coils 15 as illustrated in FIG. 1. Deflection plates 18 are oriented parallel to each other and spaced apart sufficiently for passage of all the electron beams therebetween. Deflection plates 18 are flat electrically conductive plates positioned parallel to the X-Z plane such that application of a voltage to the plates causes simultaneous deflection of the plurality of electron beams in the if-axis direction. Plates 18 are supported from the side wall of tube w by means of rigid electrical conductors 18a connected to suitable termi nals passing through the side wall. A high frequency square wave is applied across the terminals to deflection plates 18 for slightly deflecting all of the electron beams in the Y-axis direction to thereby form two sets of interlaced sweep lines on phosphor screen 13. The observer thus sees a 200 line image for a input electron beam device. As a result, 200 sensors may be utilized for providing 200 input signals and the outputs of each adjacent pair of sensors is multiplexed so that the first sensors of each pair control the intensity of the beams when all the beams are simultaneously deflected in the +Y-axis direction and the second sensors of each pair control the intensity of the same beams when all the beams are simultaneously deflected in the Y-axis driection. In this manner, the number of electron beams is reduced to a value smaller (by one half) than the number of lines in the image and still keeps the frequency response required by the multiplexing electronics in an easily achievable range as compared to attempting to multiplex all of the signals onto a single electron beam. It should be obvious that only a slight Y-axis direction deflection is required to produce the second interleaved set of 100 lines in the case of a I00 beam application. For example, if the first set of lines consists of 100 lines spaced 40 mils apart (a 4 inch raster on phosphor screen 13), the electron beams need be deflected by only 20 mils in the Y-axis direction to produce the second set of 100 lines. The frequency of the square wave signal applied to deflector plates 18, which is the frequency at which the two sets of lines (sweeps) on screen 13 switch back and forth between their two states is determined by the frequency content of the video signal to be displayed. Thus, if the video signal consists of 1 microsecond pulses, a five megahertz square wave (i.e., a switching frequency slightly above that of the signal frequency which is being displayed) would be adequate.

Referring now to FIG. 2, there is shown a front view of apertured concave electrode 1 1, partly broken away to show some of the grid structure 16 aligned directly with apertures 11b along the electron beam axes, as well as the indirectly heated cathode 12 and conductors 12c connected to the ends of the cathode heater (not shown) located interior of hollow electron emitter 12a. As indicated in FIG. 2, apertured electrode 11 is positioned in the Y-X plane when neglecting the concave curvature thereof.

FIG. 3 is an enlarged view of the electron gun portion of my multibeam cathode ray tube (i.e., the cathode grid-concave apertured electrode structure) illustrated in FIG. 1, and more clearly illustrates the orientation of the indirectly heated cathode 12 wherein a suitable ribbon 12b is positioned internally over electron-emitting tubing 12a which is heated to cause thermal emission of electrons therefrom which thence pass through holes 111) in concave electrode 11 in beam form, the beams being intensity modulated by the various imput signals applied to grids 16.

From the foregoing description, it is apparent that my invention attains the objectives set forth and makes available a new visual display device which has the capability of simultaneously displaying the outputs of a plurlaity of sensors without the need for memory cireuits or other special signal processing. My device has a high speed of operation due to the simultaneous generation of all of the sweep lines on the output phosphur screen, that is, one complete display frame is formed per sweep. Since the electrical signals to be displayed as a visual image on the phosphor screen are supplied to the multiinputs (grids 16) of my tube simultaneously instead of sequentially as required by the line-by-line scan on conventional single beam cathode ray tubes, in some applications the sweep speed in my tube may be reduced compared to the sweep speed required for a corresponding display on the conventional single-beam tube, thereby increasing the brightness of the visual display and also relaxing the bandwidth requirements of the circuits providing the input signals to the grids. My device is therefore adapted to display the input signals in substantially real time and the high speed of operation permits the viewing of objects in motion such as that of the beating human heart.

Have described a preferred embodiment of my invention, it should be apparent to those skilled in the art that various changes may be made without departing from the scope of my invention. Thus, although electrostatic type of deflector plates 18 are preferred, the resultant slight Y-axis direction deflection can also be obtained by electromagentic deflection. Thus, it is to be understood that changes may be made in the particular embodiment of my invention as described which are within the full intended scope of the invention as defined by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A multibeam visual display device comprising means for simultaneously generating a plurality of coplanar electron beams,

a like plurality of grids positioned in close proximity to said electron beam generating means and adapted to have electrical input signals applied thereto from a like plurality of signal sources such as simultaneously responsive transducers providing the electrical input signals which are in timespaced form and which intensity modulate the electron beams in accordance therewith,

a phosphor screen positioned in alignment with said electron beam generating means and spaced a substantial distance therefrom in the direction of electron beam emission therefrom,

anode means positioned between said phosphor screen and said electron beam generating means for accelerating the electrons in the electron beams along essentially straight paths intersecting at essentially a common point in the region of said anode means and crossing over in the region beyond and continuing along straight paths and focussing on said phosphor screen, and

means positioned between said anode means and said phosphor screen for simultaneously deflecting the plurality of intensity modulated electron beams in a direction normal to the plane of the electron beams in their undeflected state to thereby form on said phosphor screen a raster of a like plurality of simultaneously generated sweep lines intensity modulated by the electrical input signals to form a resultant visual image corresponding to the input signals wherein the spacings between intensity modulated points along each sweep line are in accordance with the time-spacings of the signals provided by a corresponding one of the signal sources.

2. The multibeam visual display device set forth in claim 1 and further comprising a sealed tubular member having input and output ends and fabricated of an electrically nonconductive and nonmagnetic material,

said electron beam generating means and grids supported within said tubular member adjacent the input end thereof,

said phosphor screen supported within said tubular member at the output end thereof, and

said anode means supported within said tubular member.

3. The multibeam visual display device set forth in claim 2 wherein said electron beam generating means comprise means positioned within said tubular member adjacent the input end thereof for providing a uniform source of electrons, and

a concave shaped electrode supported within said tubular member and provided with a plurality of apertures therethrough equal in number to the plurality of electron beams being generated, said concave apertured electrode in close proximity to said uniform electron source means and spaced therefrom in the direction of the tubular member output end whereby electrons emitted from said electron source means pass through the concave electrode apertures and thereby form the plurality of electron beams, said concave apertured electrode maintained at an electric potential sufficiently positive relative to said uniform electron source means to develop a desired peak magnitude of electric current of each electron beam.

4. The multibeam visual display device set forth in claim 3 wherein said plurality of grids are positioned between said uniform electron source means and the convex side of said concave electrode and aligned with the apertures therethrough along the electron beam axes.

5. The multibeam visual display device set forth in claim 1 wherein said anode means is of the electrostatic type and is adapted to be operated at a relatively high positive voltage.

6. The multibeam visual display device set forth in claim 5 wherein said anode means is cylindrically symmetrical with the device centerline axis and consists of a truncated hollow conical member fabricated of an electrically conductive material and adapted to have a positive voltage in the range of 5 to 25 kilovolts applied thereto, the electron beams passing through the hollow interior of said anode and intersecting therein,

said phosphor screen adapted to have the same voltage applied thereto as is applied to the anode whereby a field-free region exists between said anode and said phosphor screen to permit the electron beam paths to continue along their straight paths in the field-free region and thereby obtain the image on the phosphor screen which is inverted with respect to the input signals.

7. The multibeam visual display device set forth in claim 2 wherein said electron beam deflecting means is of the electromagnetic type and is supported around the outside of said tubular member.

8. The multibeam visual display device set forth in claim 2 wherein said electron beam deflecting means is of the electrostatic type and is supported within said tubular member. 9. The multibeam visual display device set forth in claim 2 and further comprising a like plurality of electrically conductive terminals passing through a side wall of said tubular member, and a like plurality of insulated electrical conductors having first ends connected to corresponding said grids and having second ends connected to corresponding said terminals whereby the plurality of input signals are applied to said grids by means of said terminals and electrical conductors. 10. The multibeam visual display device set forth in claim 9 wherein said plurality of terminals are symmetrically arranged around the circumference of said tubular member. 11. The multibeam visual display device set forth in claim 3 wherein said uniform electron source means is a single indirectly heated thermionic cathode aligned with the apertures through said concave electrode and extending the length of and conforming to the convex surface of said concave electrode. 12. The multibeam visual display device set forth in claim 3 wherein said uniform electron source means is a single directly heated strip of thermionically electron emitting material aligned with the apertures through said concave electrode and extending the length of and conforming to the convex surface of said concave electrode. 13. The multibeam visual display device set forth in claim 11 wherein said indirectly heated cathode is supported from said concave electrode. 14. The multibeam visual display device set forth in claim 3 wherein said concave electrode is of circular shape conforming to the inner circumference of said tubular member and said plurality of apertures therethrough form a single row along a diameter of the electrode which is perpendicular to the direction of deflection of electron beams by said electron beam deflecting means. 15. The multibeam visual display device set forth in claim 3 wherein said grids are supported from said concave electrode and electrically insulated therefrom. 16. The multibeam visual display device set forth in claim 15 wherein said grids each comprise a small electrically conductive washer aligned with a corresponding aperture in said concave electrode. 17. The multibeam visual display device set forth in claim 15 wherein said grids each comprise a small electrically conductive mesh having its open surface parallel to and aligned with a corresponding aperture in said concave electrode. 18. The multibeam visual display device set forth in claim 2 wherein said sealed tubular member is fabricated of glass and is evacuated to a relatively low pressure in the order of 10' torr pressure or lower. 19. The multibeam visual display device set forth in claim 2 and further comprising a pair of parallel electrostatic deflection plates posi tioned within said tubular member between said anode means and said electron beam deflecting means and oriented to generate alternating direction electric fields across said tubular member in a direction parallel to the plane of the undeflected electron beams, said pair of electrostatic deflection plates adapted to have applied thereto a high frequency square wave whereby said plurality of electron beams are slightly deflected in the directions of the generated electric fields to thereby form two sets of interlaced sweep lines and thereby obtain an image on said phosphor screen comprised of twice the plurality of sweep lines and thereby permitting the display of twice the plurality of input signals by means of multiplexing at the outputs of twice the plurality of said signal source. 20. The multibeam visual display device set forth in v claim 3 and further comprising electron beam focus electrodes supported within said tubular member and positioned between said concave electrode and said anode means and adapted to have applied thereto a voltage intermediate the voltages applied to said concave electrode and said anode means for improving concentricity of spherical equipotentials developed in the region between said concave electrode and said anode means thereby causing the electron beams more precisely follow the straight paths from said concave electrode to said anode means. 21. The multibeam visual display device set forth in claim 14 wherein said plurality of apertures consist of at least 20 equally spaced apart apertures, and the resultant visual image formed on said phosphor screen in the case of the simultaneously responsive transducers corresponds to sensed time-spaced signals received thereby and converted into the timespaced electrical input signals wherein the spacings between intensity modulated points along each sweep line are in accordance with the times of arrival of the sensed time-spaced signals at a corresponding one of the transducers. 

1. A multibeam visual display device comprising means for simultaneously generating a plurality of coplanar electron beams, a like plurality of grids positioned in close proximity to said electron beam generating Means and adapted to have electrical input signals applied thereto from a like plurality of signal sources such as simultaneously responsive transducers providing the electrical input signals which are in time-spaced form and which intensity modulate the electron beams in accordance therewith, a phosphor screen positioned in alignment with said electron beam generating means and spaced a substantial distance therefrom in the direction of electron beam emission therefrom, anode means positioned between said phosphor screen and said electron beam generating means for accelerating the electrons in the electron beams along essentially straight paths intersecting at essentially a common point in the region of said anode means and crossing over in the region beyond and continuing along straight paths and focussing on said phosphor screen, and means positioned between said anode means and said phosphor screen for simultaneously deflecting the plurality of intensity modulated electron beams in a direction normal to the plane of the electron beams in their undeflected state to thereby form on said phosphor screen a raster of a like plurality of simultaneously generated sweep lines intensity modulated by the electrical input signals to form a resultant visual image corresponding to the input signals wherein the spacings between intensity modulated points along each sweep line are in accordance with the time-spacings of the signals provided by a corresponding one of the signal sources.
 2. The multibeam visual display device set forth in claim 1 and further comprising a sealed tubular member having input and output ends and fabricated of an electrically nonconductive and nonmagnetic material, said electron beam generating means and grids supported within said tubular member adjacent the input end thereof, said phosphor screen supported within said tubular member at the output end thereof, and said anode means supported within said tubular member.
 3. The multibeam visual display device set forth in claim 2 wherein said electron beam generating means comprise means positioned within said tubular member adjacent the input end thereof for providing a uniform source of electrons, and a concave shaped electrode supported within said tubular member and provided with a plurality of apertures therethrough equal in number to the plurality of electron beams being generated, said concave apertured electrode in close proximity to said uniform electron source means and spaced therefrom in the direction of the tubular member output end whereby electrons emitted from said electron source means pass through the concave electrode apertures and thereby form the plurality of electron beams, said concave apertured electrode maintained at an electric potential sufficiently positive relative to said uniform electron source means to develop a desired peak magnitude of electric current of each electron beam.
 4. The multibeam visual display device set forth in claim 3 wherein said plurality of grids are positioned between said uniform electron source means and the convex side of said concave electrode and aligned with the apertures therethrough along the electron beam axes.
 5. The multibeam visual display device set forth in claim 1 wherein said anode means is of the electrostatic type and is adapted to be operated at a relatively high positive voltage.
 6. The multibeam visual display device set forth in claim 5 wherein said anode means is cylindrically symmetrical with the device centerline axis and consists of a truncated hollow conical member fabricated of an electrically conductive material and adapted to have a positive voltage in the range of 5 to 25 kilovolts applied thereto, the electron beams passing through the hollow interior of said anode and intersecting therein, said phosphor screen adapted to have the same voltage applied thereto as is applied to the anode whereby a field-free region exists between saiD anode and said phosphor screen to permit the electron beam paths to continue along their straight paths in the field-free region and thereby obtain the image on the phosphor screen which is inverted with respect to the input signals.
 7. The multibeam visual display device set forth in claim 2 wherein said electron beam deflecting means is of the electromagnetic type and is supported around the outside of said tubular member.
 8. The multibeam visual display device set forth in claim 2 wherein said electron beam deflecting means is of the electrostatic type and is supported within said tubular member.
 9. The multibeam visual display device set forth in claim 2 and further comprising a like plurality of electrically conductive terminals passing through a side wall of said tubular member, and a like plurality of insulated electrical conductors having first ends connected to corresponding said grids and having second ends connected to corresponding said terminals whereby the plurality of input signals are applied to said grids by means of said terminals and electrical conductors.
 10. The multibeam visual display device set forth in claim 9 wherein said plurality of terminals are symmetrically arranged around the circumference of said tubular member.
 11. The multibeam visual display device set forth in claim 3 wherein said uniform electron source means is a single indirectly heated thermionic cathode aligned with the apertures through said concave electrode and extending the length of and conforming to the convex surface of said concave electrode.
 12. The multibeam visual display device set forth in claim 3 wherein said uniform electron source means is a single directly heated strip of thermionically electron emitting material aligned with the apertures through said concave electrode and extending the length of and conforming to the convex surface of said concave electrode.
 13. The multibeam visual display device set forth in claim 11 wherein said indirectly heated cathode is supported from said concave electrode.
 14. The multibeam visual display device set forth in claim 3 wherein said concave electrode is of circular shape conforming to the inner circumference of said tubular member and said plurality of apertures therethrough form a single row along a diameter of the electrode which is perpendicular to the direction of deflection of electron beams by said electron beam deflecting means.
 15. The multibeam visual display device set forth in claim 3 wherein said grids are supported from said concave electrode and electrically insulated therefrom.
 16. The multibeam visual display device set forth in claim 15 wherein said grids each comprise a small electrically conductive washer aligned with a corresponding aperture in said concave electrode.
 17. The multibeam visual display device set forth in claim 15 wherein said grids each comprise a small electrically conductive mesh having its open surface parallel to and aligned with a corresponding aperture in said concave electrode.
 18. The multibeam visual display device set forth in claim 2 wherein said sealed tubular member is fabricated of glass and is evacuated to a relatively low pressure in the order of 10 5 torr pressure or lower.
 19. The multibeam visual display device set forth in claim 2 and further comprising a pair of parallel electrostatic deflection plates positioned within said tubular member between said anode means and said electron beam deflecting means and oriented to generate alternating direction electric fields across said tubular member in a direction parallel to the plane of the undeflected electron beams, said pair of electrostatic deflection plates adapted to have applied thereto a high frequency square wave whereby said plurality of electron beams are slightly deflected in the directions of the generated electric fields to thereby form two sets of interlaced sweep lines and thereby obtain an Image on said phosphor screen comprised of twice the plurality of sweep lines and thereby permitting the display of twice the plurality of input signals by means of multiplexing at the outputs of twice the plurality of said signal source.
 20. The multibeam visual display device set forth in claim 3 and further comprising electron beam focus electrodes supported within said tubular member and positioned between said concave electrode and said anode means and adapted to have applied thereto a voltage intermediate the voltages applied to said concave electrode and said anode means for improving concentricity of spherical equipotentials developed in the region between said concave electrode and said anode means thereby causing the electron beams more precisely follow the straight paths from said concave electrode to said anode means.
 21. The multibeam visual display device set forth in claim 14 wherein said plurality of apertures consist of at least 20 equally spaced apart apertures, and the resultant visual image formed on said phosphor screen in the case of the simultaneously responsive transducers corresponds to sensed time-spaced signals received thereby and converted into the time-spaced electrical input signals wherein the spacings between intensity modulated points along each sweep line are in accordance with the times of arrival of the sensed time-spaced signals at a corresponding one of the transducers. 